For me, the ability to split tone and/ or blend the various curves alone is worth it. Easier to find the tone you want and split toning adds a whole other level. I also believe that the QTR curves try to use less color ink then ABW and/or print in color with profiles. I scanned and enlarged test prints years ago, and as I recall, it was easy to see when you enlarged enough to see the individual dots. This should in theory lead to less tone shift in the future. I have always used one of the existing curves and relinearized for the paper I was using, but the reality is that the changes I ended up making were frequently quite small. I think you would be fine using existing curves most of the time. If you are looking for huge differences in print quality between QTR and ABW, you may be disappointed. For me it is more subtle, but real. In addition, the ability to get "under the hood" in various ways has been useful for me, but perhaps less for others.
